The production of disposable fabrics, including wet wipes, disposable diapers, incontinent garments, and feminine care products, is constantly studied. However, one of the major problems is to create an economical coherent fibrous web, which will easily dissolve or disintegrate in water, while still maintaining in-use strength. Without such an in-use strength, such a product could not be easily used and pulled from its package, and without its dissolvability properties, it would not be possible or advisable to dispose of it by simply flushing it down the toilet.
Disposable fabrics can be used in various ways, such as disposable wipes, and can be incorporated in other products, such as diapers, feminine care products, and adult incontinent care products. Said fabrics are typically formed by wet or dry (air) laying a generally random plurality of fibers and joining them together to form a coherent web with a binder. However, known binders tend not to degrade, thus preventing or diminishing the degradation of the disposable product. Several laying technologies are known in the art, for example, wet-laying, air-laying, or carding. Bonding technologies are also known in the art, e.g. latex bonding, thermo-bonding fibers, or hydro-entanglement by water jets. Often, the nonwoven fabric is carded and bonded by hydro-entanglement, a technology known as Spunlace.
Accordingly, there is a need for binder compositions with improved hard water solubility. Several polymers are known to exhibit cloud points or inverse solubility properties in aqueous media, e.g. as wound dressings with good absorbing characteristics and easy removal (JP 6233809), and as materials in flushable personal care products (U.S. Pat. No. 5,509,913).
Other known binders are ion-sensitive binders. For example, U.S. Pat. No. 5,312,883, U.S. Pat. No. 5,317,063, U.S. Pat. No. 5,384,189 and EP 608460, disclose ion-sensitive polymers based on acrylic acid and alkyl acrylates. However, these binders are not soluble in water containing more than 15 ppm calcium and/or magnesium ions. Notably, U.S. Pat. No. 5,312,883 discloses terpolymers as suitable binders for flushable nonwoven webs.
U.S. Pat. No. 6,423,804 and U.S. Pat. No. 6,429,261 describe the incorporation of sulfonic groups (soft base) into the polymer chain together with carboxylic groups (hard base). These binders are insoluble in a solution containing 2-5% sodium chloride.
Although various ion and temperature sensitive compositions for flushable materials are known, there still exists a need for flushable products having tap water-disintegration in soft and hard water areas, and at the same time having improved strength for better processability and use properties. The binder, to be practically useful, is needed at a reasonable cost without compromising product safety and environmental concerns, something that past and present products fail to do. Moreover, there is a need for flushable products possessing softness, resiliency, and fiber dispersion after toilet flushing so that fibers do not become entangled with obstacles in municipal drain-lines, conveyance and waste treatment systems.
Accordingly, it is an object of the present invention to provide a flushable nonwoven fabric, which comprises an ion-sensitive binder polymer composition that overcomes the drawbacks of the prior art.
It is also an object of the present invention to provide an ion-sensitive binder polymer composition which is insoluble in a salt solution containing about 2 to 5 weight % monovalent or multivalent ions, and which is soluble in tap water containing more than 15 ppm calcium and/or magnesium ions.
It is another object of the invention to use said binder polymer compositions in the manufacture of flushable, nonwoven fabrics. Furthermore, said fabrics can be used to prepare various articles.
The above and other objects and advantages of invention will become apparent as the description proceeds.